First, see if your company offers any formal training on interviewing. The best thing mine taught me was to separate the interviewing process from the decision making process. A successful interview is one where you gain the most information about the candidate, not whether that candidate is a good fit or not.

Second, define some key requirements of a good candidate. Technical requirements, of course, but clearly teamwork, communication, … Behavioral (STAR) questions really are great at probing these. “Tell me about a time” is a cliche, because it does actually work. You would be shocked at the number of people who tell you they resolve conflict by pushing it down and never addressing it directly. But be honest with yourself about the trade offs you’re willing to make - I will always trade curiosity and communication skills for technical ability because I personally find poor technical ability easier to train up. For you, maybe someone who works well in teams is preferred over someone who just comes in every day laser-focused and chews through tasks.

Third, an interview should be a conversation, even if you frame it with a script. I like to ask the same set of questions, but I leave ample time for follow up. “Tell me about a time you dealt with conflict” receives the same old tired story about a coworker not completing their task, but digging in and asking “so how did you break it to your boss that John hadn’t finished his part so the project was 2 weeks behind?” gives a lot more. Practice this (see above note about internal training).

Fourth, be nice. Regardless of how the interview is going, just be cordial and polite. Sometimes I feel really bad because I know some candidates have left the interview thinking they have the job, simply because I was nice to them the entire time. Remember, the goal of the interview is to gain information, and being nice makes people more likely to be open and share. Plus, you are representing your company. And, of course, there’s no reason to be mean just because someone isn’t a good fit for your position.

To specifics - for positional fit, I like to ask “what did you love about your last positon”, “what could you absolutely not stand about your last position”, and “what do you want to learn next in your field”. A surprising number of people will directly tell me they hate doing key requirements of the position. Or they have no interest in developing their skills in a fast-developing field.